package org.zoyi.util;

import java.io.*;
import java.util.Random;
import java.util.*;

public class Authcode {

	public enum DiscuzAuthcodeMode {
		Encode, Decode
	};

	/// <summary>
	/// 从字符串的指定位置截取指定长度的子字符串
	/// </summary>
	/// <param name="str">原字符串</param>
	/// <param name="startIndex">子字符串的起始位置</param>
	/// <param name="length">子字符串的长度</param>
	/// <returns>子字符串</returns>
	public static String CutString(String str, int startIndex, int length) {
		if (startIndex >= 0) {
			if (length < 0) {
				length = length * -1;
				if (startIndex - length < 0) {
					length = startIndex;
					startIndex = 0;
				} else {
					startIndex = startIndex - length;
				}
			}

			if (startIndex > str.length()) {
				return "";
			}

		} else {
			if (length < 0) {
				return "";
			} else {
				if (length + startIndex > 0) {
					length = length + startIndex;
					startIndex = 0;
				} else {
					return "";
				}
			}
		}

		if (str.length() - startIndex < length) {

			length = str.length() - startIndex;
		}

		return str.substring(startIndex, startIndex + length);
	}

	/// <summary>
	/// 从字符串的指定位置开始截取到字符串结尾的了符串
	/// </summary>
	/// <param name="str">原字符串</param>
	/// <param name="startIndex">子字符串的起始位置</param>
	/// <returns>子字符串</returns>
	public static String CutString(String str, int startIndex) {
		return CutString(str, startIndex, str.length());
	}

	/// <summary>
	/// 返回文件是否存在
	/// </summary>
	/// <param name="filename">文件名</param>
	/// <returns>是否存在</returns>
	public static boolean FileExists(String filename) {
		File f = new File(filename);
		return f.exists();
	}

	/// <summary>
	/// MD5函数
	/// </summary>
	/// <param name="str">原始字符串</param>
	/// <returns>MD5结果</returns>
	public static String MD5(String str) {
		return MD5Generator.MD5(str);
	}

	/// <summary>
	/// 字段串是否为Null或为""(空)
	/// </summary>
	/// <param name="str"></param>
	/// <returns></returns>
	public static boolean StrIsNullOrEmpty(String str) {
		//#if NET1
		if (str == null || str.trim().equals("")) {
			return true;
		}

		return false;
	}

	/// <summary>
	/// 用于 RC4 处理密码
	/// </summary>
	/// <param name="pass">密码字串</param>
	/// <param name="kLen">密钥长度，一般为 256</param>
	/// <returns></returns>
	static private byte[] GetKey(byte[] pass, int kLen) {
		byte[] mBox = new byte[kLen];

		for (int i = 0; i < kLen; i++) {
			mBox[i] = (byte) i;
		}

		int j = 0;
		for (int i = 0; i < kLen; i++) {

			j = (j + (int) ((mBox[i] + 256) % 256) + pass[i % pass.length])
					% kLen;

			byte temp = mBox[i];
			mBox[i] = mBox[j];
			mBox[j] = temp;
		}

		return mBox;
	}

	/// <summary>
	/// 生成随机字符
	/// </summary>
	/// <param name="lens">随机字符长度</param>
	/// <returns>随机字符</returns>
	public static String RandomString(int lens) {
		char[] CharArray = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k',
				'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
				'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
		int clens = CharArray.length;
		String sCode = "";
		Random random = new Random();
		for (int i = 0; i < lens; i++) {
			sCode += CharArray[Math.abs(random.nextInt(clens))];
		}
		return sCode;
	}

	/// <summary>
	/// 使用 Discuz authcode 方法对字符串加密
	/// </summary>
	/// <param name="source">原始字符串</param>
	/// <param name="key">密钥</param>
	/// <param name="expiry">加密字串有效时间，单位是秒</param>
	/// <returns>加密结果</returns>
	public static String authcodeEncode(String source, String key, int expiry) {
		return authcode(source, key, DiscuzAuthcodeMode.Encode, expiry);

	}

	/// <summary>
	/// 使用 Discuz authcode 方法对字符串加密
	/// </summary>
	/// <param name="source">原始字符串</param>
	/// <param name="key">密钥</param>
	/// <returns>加密结果</returns>
	public static String authcodeEncode(String source, String key) {
		return authcode(source, key, DiscuzAuthcodeMode.Encode, 0);

	}

	/// <summary>
	/// 使用 Discuz authcode 方法对字符串解密
	/// </summary>
	/// <param name="source">原始字符串</param>
	/// <param name="key">密钥</param>
	/// <returns>解密结果</returns>
	public static String authcodeDecode(String source, String key) {
		return authcode(source, key, DiscuzAuthcodeMode.Decode, 0);

	}

	/// <summary>
	/// 使用 变形的 rc4 编码方法对字符串进行加密或者解密
	/// </summary>
	/// <param name="source">原始字符串</param>
	/// <param name="key">密钥</param>
	/// <param name="operation">操作 加密还是解密</param>
	/// <param name="expiry">加密字串过期时间</param>
	/// <returns>加密或者解密后的字符串</returns>
	private static String authcode(String source, String key,
			DiscuzAuthcodeMode operation, int expiry) {
		try {
			if (source == null || key == null) {
				return "";
			}

			int ckey_length = 4;
			String keya, keyb, keyc, cryptkey, result;


			key = MD5(key);

			keya = MD5(CutString(key, 0, 16));

			keyb = MD5(CutString(key, 16, 16));

			keyc = ckey_length > 0 ? (operation == DiscuzAuthcodeMode.Decode ? CutString(
					source, 0, ckey_length)
					: RandomString(ckey_length))
					: "";


			cryptkey = keya + MD5(keya + keyc);

			if (operation == DiscuzAuthcodeMode.Decode) {
				byte[] temp;
				
				temp = Base64.decode(CutString(source, ckey_length));
				result = new String(RC4(temp, cryptkey));
				if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
					return CutString(result, 26);
				} else {
					temp = Base64.decode(CutString(source+"=", ckey_length));
					result = new String(RC4(temp, cryptkey));
					if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
						return CutString(result, 26);
					} else {
						temp = Base64.decode(CutString(source+"==", ckey_length));
						result = new String(RC4(temp, cryptkey));
						if (CutString(result, 10, 16).equals(CutString(MD5(CutString(result, 26) + keyb), 0, 16))) {
							return CutString(result, 26);
						}else{
							return "2";
						}
					}
				}
			} else {
				source = "0000000000" + CutString(MD5(source + keyb), 0, 16)
						+ source;

				byte[] temp = RC4(source.getBytes("UTF-8"), cryptkey);

				return keyc + Base64.encode(temp);

			}
		} catch (Exception e) {
			return "";
		}

	}

	// / <summary>
	// / RC4 原始算法
	// / </summary>
	// / <param name="input">原始字串数组</param>
	// / <param name="pass">密钥</param>
	// / <returns>处理后的字串数组</returns>
	private static byte[] RC4(byte[] input, String pass) {
		if (input == null || pass == null)
			return null;

		byte[] output = new byte[input.length];
		byte[] mBox = GetKey(pass.getBytes(), 256);

		// 加密
		int i = 0;
		int j = 0;

		for (int offset = 0; offset < input.length; offset++) {
			i = (i + 1) % mBox.length;
			j = (j + (int) ((mBox[i] + 256) % 256)) % mBox.length;

			byte temp = mBox[i];
			mBox[i] = mBox[j];
			mBox[j] = temp;
			byte a = input[offset];

			//byte b = mBox[(mBox[i] + mBox[j] % mBox.Length) % mBox.Length];
			// mBox[j] 一定比 mBox.Length 小，不需要在取模
			byte b = mBox[(toInt(mBox[i]) + toInt(mBox[j])) % mBox.length];

			output[offset] = (byte) ((int) a ^ (int) toInt(b));
		}

		return output;
	}

	public static int toInt(byte b) {
		return (int) ((b + 256) % 256);
	}

	public long getUnixTimestamp() {
		Calendar cal = Calendar.getInstance();
		return cal.getTimeInMillis() / 1000;
	}

	public static void main(String[] args) {
		String test = "fire";
		String key = "123456";
		String afStr = Authcode.authcodeEncode(test, key);
		System.out.println("--------encode:" + afStr);
		//String deStr = Authcode.authcodeDecode("66afE5LwHoO2JNQ3P9OqTsgNv07OZSfylhACahWUgOafwdJJ%2FUadZJ1pbhEKwrU9lOsGSnoHAV8tZdM0OGGT", key);
		//System.out.println(":"+deStr);

	}

}